More of the same. This post (http://forums.rockbox.org/index.php?topic=4252.msg31623#msg31623) mentions a similar bug:
[code]Also, if I create my own entry ("80's" artist ? year ^ "198" : album ? year ^ "198" : title) I get an artist listing for every song that artist has. For example, AH-HA has only one song (Take On Me) and shows up only once in the artist list, however U2 has over 200 songs on my ipod and is listed as many times in the artist screen.[/code]
This doesn't appear to be the current behaviour, but there are still some duplicate artist entries using the search string above

In summary, the searching and filtering by year seems flaky and perhaps needs a tidy up?